We report the design, fabrication, and characterization of colloidal PbSe nanocrystal (NC)-based photovoltaic test structures that exhibit an excitonic solar cell mechanism. Charge extraction from the NC active layer is driven by a photoinduced chemical potential energy gradient at the nanostructured heterojunction. By minimizing perturbation to PbSe NC energy levels and thereby gaining insight into the "intrinsic" photovoltaic properties and charge transfer mechanism of PbSe NC, we show a direct correlation between interfacial energy level offsets and photovoltaic device performance. Size dependent PbSe NC energy levels were determined by cyclic voltammetry and optical spectroscopy and correlated to photovoltaic measurements. Photovoltaic test structures were fabricated from PbSe NC films sandwiched between layers of ZnO nanoparticles and PEDOT:PSS as electron and hole transporting elements, respectively. The device current-voltage characteristics suggest a charge separation mechanism that Is distinct from previously reported Schottky devices and consistent with signatures of excitonic solar cells. Remarkably, despite the limitation of planar junction structure, and without film thickness optimization, the best performing device shows a 1-sun power conversion efficiency of 3.4%, ranking among the highest performing NC-based solar cells reported to date. © 2009 American Chemical Society.
|Original language||English (US)|
|Number of pages||7|
|State||Published - Nov 11 2009|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This work was supported by Cornell Center for Materials Research SEED fund. J.J.C. acknowledges support from the NSF IGERT fellowship. Y.F.L. acknowledges fellowship from Agency of Science, Technology and Research (A*STAR), Singapore. M.B.S. acknowledges financial support from the Provost's Academic Diversity Postdoctoral Fellowship from Cornell University. L.S. acknowledges support from NYSTAR. M.O. acknowledges support from Cornell Presidential Research Scholars undergraduate research fellowship. A.G. acknowledges support from the KAUST-CU center for energy and sustainability.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.